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Spindle Box CAD System Based on Object-Oriented Thought
**Abstract:**
This paper presents a Computer-Aided Design (CAD) system for the headstock of a numerical control boring (milling) machine. The system is built using object-oriented programming principles, enabling efficient calculation of dynamic parameters and the creation of a three-dimensional solid model library. The system offers advantages such as ease of use, high automation, and scalability, significantly improving design efficiency while reducing both design and production costs. It also enhances product quality and contributes to greater economic benefits.
**Keywords:** Object-oriented; Headstock; Parametric feature modeling; Polymorphism; Inheritance
**Classification Number:** TP391.72
**Document Code:** A
**Article ID:** 1001-2265 (2000) 02-0011-03
**1 Introduction**
The WHZ-02X series CNC boring (milling) bed from Wuhu Heavy Duty Machine Tool Factory is a multi-variety, low-volume product, typically customized based on user and market demands. Due to frequent modifications in this production model, the main drive system—which is one of the most frequently changed components—has traditionally been designed manually. This approach was time-consuming, inefficient, and unable to keep up with rapid market changes. Additionally, it lacked quantitative analysis, limiting the overall improvement of the design process. To enhance competitiveness, it is essential to implement a rapid and parallel design approach for the CNC spindle (milling) headstock. This paper introduces a comprehensive product modeling system that integrates object-oriented thinking to create an effective CAD environment, enabling quick responses to changing market and user needs.
**2 Overall System Framework Design**
The system calculates the main cutting force and power based on input parameters like maximum stroke, rotation speed, and workpiece diameter, allowing for fast machine tool design. By querying a 3D machine type spectrum library, similar designs are retrieved to guide new projects. Using Visual C++, an object-oriented language, the system supports interface design and dynamic parameter calculations, incorporating data abstraction, encapsulation, and modularity. The system includes modules such as raw data input, cutting force/power calculation, and result output, enhancing its reliability. A top-down, assembly-oriented full-correlation parallel design (DFA) approach is used to generate part drawings from assembly diagrams, building a parametric graphic library. This reflects the core idea of object-oriented design, creating a 3D solid model of the headstock. The system framework is illustrated in Figure 1.
**Figure 1: CAD System Framework Design for Boring (Milling) Headstock**
After implementation, the main process interface is shown in Figure 2. Users can select processing methods from the main menu, input relevant parameters, and view the corresponding calculation results on the screen.
**Figure 2: Main Process Interface of Spindle Head CAD System**
**3 CAD System Structure and Operation Logic of Numerical Control Boring (Milling) Headstock**
**3.1 Dynamic Parameter Calculation Module**
This module computes tangential, radial, and axial cutting forces, as well as cutting power for various operations such as turning, boring, milling, drilling, and reaming. Each operation has unique influencing factors, such as material hardness, cutting speed, and tool geometry, leading to different formulas. To manage these complexities, the system uses a document/window architecture with classes defined via ClassWizard. These include dialogue classes for inputting parameters and calculation result classes for output. Member functions like Drawresult() and Serialize() facilitate data exchange between documents and dialogues. Multiple document types are used to compare results from different inputs, and each calculation result class is linked to the document class for efficient data management. The software framework is shown in Figure 3.
**Figure 3: Dynamic Parameter Calculation Framework**
**3.2 Establishment of Three-Dimensional Solid Graphic Library of Spindle Head**
**3.2.1 Uniqueness and Classification**
Each component in the headstock has a unique name and is classified into sub-assemblies. The headstock connects the motor and spindle, transferring power, controlling speed, and enabling motion control. Based on functional requirements, the spindle box is divided into major components such as the spindle, transmission mechanism, motor shaft, cylinder, and housing. These sub-assemblies are designed in parallel under overall constraints, with each unit further decomposed into smaller parts. The speed change mechanism is broken down into axes and their components, eventually forming known shape features or part units.
**3.2.2 Polymorphism and Inheritance**
In object-oriented design, polymorphism allows different objects to interpret the same message in different ways. Inheritance enables lower-level assemblies to inherit design constraints from higher levels. For example, the shift fork’s hole dimensions are inherited from previous layers and must be respected without modification. If these dimensions change, related parameters such as total length and width adjust accordingly. Polymorphism also allows the same sub-assembly to use different structural constraints when combined with other parts, offering flexibility in design. The classification, polymorphism, and constraint diversity of sub-assemblies are illustrated in Figure 5.
**Figure 5: Diversity, Polymorphism, and Structural Constraints of Subassemblies in the Headstock**
**4 Conclusion**
This paper demonstrates the use of Visual C++ to calculate dynamic parameters and apply object-oriented concepts such as inheritance, polymorphism, and encapsulation to build a CAD system for the headstock. The system improves scalability and stability, laying a strong foundation for future integration with CAM and CAE systems.